^ + if you were, in fact, accepted, there will be a drop down box in the details of your car info.
Go: Entry Forms, Select your race, select your team (not accepted won't get any further than this), enter your captain's email and password, then log in to the details page.
Last time I checked, numbers 00 - 999 were available.
Choose one of those.
You can change it as often as you like so long as no other team has taken your favorite number, in which case, you might break down, sob and then try to contact that team to buy it from them in beer and plundered booty.
-Kyle
Eyesore Racing
"That's probably wrong, but it's worth a shot."